Applicants hereby claim foreign priority benefits to Japanese Patent Application No. 2000-189148, filed Jun. 23, 2000.
1. Technical Field
The present invention relates to a device and method for solder-ball bonding a bonding pad formed on a slider on which a head is placed with a lead pad formed at an end of the lead in a head gimbal assembly, which is a constituting part of a hard disk device.
2. Description of the Related Art
Referring now to FIGS. 8 and 9, a head gimbal (HG) assembly 100 is configured of an actuator arm 101 that has an opening 102, and a load beam 104 that extends from the central portion of the flat portion 103 of the actuator arm 101 in the lengthwise direction, to which a part that overlaps the actuator arm 101 is welded. The opening 102 is used when the HG assembly 100 is pivotably held by the HG assembly holder of a magnetic disk device (not shown), and the HG assembly 100 pivots around a virtual axis 150 that passes through the center of the opening 102 substantially vertically to the flat portion 103 in the directions of arrows A and B.
A mounting plate 105 is welded over the nearly central portion of a load beam 104, and flexure 106 is disposed over the center-to-end portion of the load beam 104. The half of the flexure 106 on the side of the mounting plate 105 is welded to the load beam 104, but the end-side half is not welded.
As FIG. 8 shows, an arch-shaped opening 107 is formed on the end portion of the flexure 106, and a slider 109 is fixed by bonding on the flexure tongue 106a (FIG. 9) projecting from the platform 108 in the endmost portion of the flexure 106 toward the center of the arch-shaped opening 107. The flexure tongue 106a is held at a point in the position corresponding to the central portion of the slider 109 by a pivot 104a projecting from the load beam 104 (shown by a broken line in FIG. 9). Thereby the slider 109 can be tilted in relative to the load beam 104 at a predetermined angle (often called pitch, roll, or yaw) in all directions.
Parts of four leads 110 to 113 are laid along the extension 105a that extends from the mounting plate 105, and fixed to the extension 105a via an insulating sheet not to contact to each other. The one end of the extension 105a forms a multi-connector 114.
The four leads 110 to 113 are laid on the mounting plate 105 and the flexure 106 in the pattern shown in FIG. 7, and similarly fixed to them via insulating sheets not to contact to each other. The other end of each lead is floated in the arch-shaped opening 107 as shown in FIG. 8, and each of two leads is bent in a crank shape in pairs and reaches the platform 108.
Here, the paired leads are bent substantially perpendicularly so as to face the front surface 109a of the slider 109 through two openings 114 and 115 formed between the platform 108 and the flexure tongue 106a (FIG. 9), and form lead pads 110a to 113a corresponding to pad-bonding surfaces of four bonding pads 116 to 119 formed on the front surface 109a, respectively. The four leads 110 to 113 are fixed to the platform 108 through an insulating sheet 120 near the end portions. The portion other than the slider 109 of the above-described HG assembly corresponds to the slider holding means.
Next, the method for electrically connecting the four bonding pads 116 to 119 with correspondingly formed lead pads 110a to 113a using a conventional solder-ball bonding device will be described. FIG. 9 shows a schematic diagram of a conventional solder-ball bonding device. The optical system 131 that configures the solder-ball bonding device 130 inputs laser beam generated by a laser oscillator (not shown) through optical fibers 132, passes the laser beam through a condenser lens system for condensing the laser beam to converged beam, and outputs the converged beam to the hollow portion 134a of a capillary 134 through a laser-beam path 133a of the solder-ball feeder 133.
The hollow portion 134a of a capillary 134 mounted to the solder-ball feeder 133 is a path of the converged laser beam, as well as a solder-ball supplying path as described later. The tip of the capillary 134 is cut into a wedge shape, and forms a discharging opening 134b led to the hollow portion 134a. The solder-ball feeder 133 comprises a laser-beam path 133a that connects the optical system 131 and the hollow portion 134a of the mounted capillary 134, a stocker 133b for stocking a plurality of solder balls 135, a solder-ball transporting disc 133c that is rotatably held in the solder-ball feeder 133 by driving means (not shown), an introducing pipe 133d for introducing nitrogen gas N2 from a nitrogen-gas cylinder 8 (not shown) through a tube 136, and a ventilating path 133e for guiding the introduced nitrogen gas N2 to the laser-beam path 133a. 
The solder-ball transporting disc 133c has a predetermined number of solder-ball accommodating holes 133f equidistantly formed on the circumference of a predetermined radius from the center of rotation, and a solder-ball accommodating hole 133f accommodates a solder ball 135 that falls when the solder-ball accommodating hole 133f is moved to the position that coincides with the hole (not shown) formed on the bottom of the stocker 133b. When the solder-ball transporting disc 133c rotates and the solder-ball accommodating hole 133f that accommodates a solder ball is moved into the ventilating path 133e, the solder ball 135 falls automatically, and is fed into the capillary 134 by nitrogen gas N2 that is flowing in the arrow direction in the ventilating path 133e. 
The solder-ball transporting disc 133c is so configured that another solder-ball accommodating hole 133f formed on the solder-ball transporting disc 133c is then moved to the position that coincides with the hole (not shown) formed on the bottom of the stocker 133b. Thus, each time the solder-ball transporting disc 133c rotates by a predetermined angle in the timing described below, the above-described transportation is repeated, and a solder ball is fed into the capillary 134.
The solder-ball bonding device 130 configured as described above is held by a transporter (not shown) slidably in the F-G direction (vertical direction), which can utilize gravity. On the other hand, on solder-ball bonding, as FIG. 9 shows, the HG assembly 100 is held by a holder (not shown) so that the pad bonding surface 118a of the bonding pad 118 is substantially perpendicular to the bonding surface 112b of the lead pad 112a, and so that each of them is tilted by about 45 degrees to the above described F-G direction.
The partial sectional view of the HG assembly 100 in FIG. 9 corresponds to the sectional view of the cross section in FIG. 8 along the line 151 that passes through the center of the bonding pad 118 viewed from the direction of the arrow C. The HG assembly 100 and the solder-ball bonding device 130 thus held are relatively positioned so that the tip of the capillary 134 equidistantly approaches the bonding pad 118 and the lead pad 112a when the solder-ball bonding device 130 moves a predetermined distance in the G direction as FIG. 9 shows.
When solder-ball bonding is carried out in the above-described configuration, the tip of the capillary 134 is first positioned most close to the pad bonding surface 118a of the bonding pad 118 and the bonding surface 112b of the lead pad 112a, but does not touch these as FIG. 9 shows.
Next, the solder-ball transporting disc 133c is rotated by a predetermined angle to feed a solder ball 135 into the capillary 134 through the N2-gas ventilating path 133e. This solder ball 135 falls in the capillary 134, and is guided by the discharging opening 134b until it stops at the position where it touches the pad bonding surface 118a of the bonding pad 118 and the bonding surface 112b of the lead pad 112a. During this time, nitrogen gas N2 is injected from the introducing pipe 133d into the capillary 134 at the predetermined flow rate to promote falling of the solder ball 135, and the ball 135 is weakly pushed against the above-described surfaces by the gas pressure.
Laser beams are generated in this state. In this time, converged laser beams 137 are partly reflected by the inner wall of the hollow portion 134a of the capillary 134 and radiated to the solder ball 135. The solder ball 135 is melted by this laser radiation, and wets the pad bonding surface 118a of the bonding pad 118 and the bonding surface 112b of the lead pad 112a to form solder-bonded portion. The pad bonding surface 118a of the bonding pad 118 and the bonding surface 112b of the lead pad 112a correspond to the connecting portion where the solder-bonded portion is formed. In this time, nitrogen gas N2 that flows out acts to push the molten solder against each bonding surface, as well as to cover the solder to prevent the oxidation thereof.
Also, when three connecting portions formed by the pairs of other bonding pads and lead pads are solder-bonded, the solder-ball bonding device 130 or the HG assembly 100 is moved in the predetermined directions to change the relative positions so that the desired connecting portion faces the discharging opening 134b of the capillary 134, and the solder-bonded portion is formed by the same bonding operations.
Problems to be Solved by the Invention
As described above, since the conventional solder-ball bonding device is configured so as to perform (1) the supply of solder balls, (2) the positioning of a solder ball, (3) the blowing of nitrogen gas N2, and (4) the melting of the solder ball by laser radiation in one device, there are various problems.
For example, since the optical system has spatial restriction, the laser energy is reduced to xc2xc in the stage where the laser beams from the optical system 131 enter the laser-beam path 133a of the solder-ball feeder 133, and further reduced to ⅕ in the stage where the laser beams are reflected in the capillary 134 and reach the discharging opening 134b. That is, the laser energy radiated onto a solder ball is reduced to about {fraction (1/20)} of the laser energy outputted from the optical fiber 132.
Also, since various functions are integrated, the entire device must be overhauled even when only a part of the device does not work well. In such a case, the reconditioning of the entire device is required after repairing, and the maintenance of the device is cumbersome.
Furthermore, since the weight of the device itself is large, the device is not suited to the positioning method by moving the whole device when relative positioning with the HG assembly is performed. In addition, since all the operations are conducted in one device, the procedures of operations are fixed, and the efficiency cannot be improved by improving the procedures of operations.
Therefore, one object of the present invention is to provide a solder-ball bonding device that has an improved laser radiating efficiency for the reflow of solder balls, that is easy to maintain, and that excels in workability.
In order to connect a first bonding surface to a second bonding surface, the first bonding surface being on a pad formed on a slider held by slider holding means of a disk device, the second bonding surface being on a pad formed on an end of a lead set on the slider holding means, and the second bonding surface being set substantially perpendicularly to and close to a surface including the first bonding surface, the solder-ball bonding device according to the present invention comprises a solder-ball holder that has a stocker to stock a plurality of solder balls and ball holding holes to hold balls supplied from the stocker in predetermined positions, the solder ball holder being set in a position at a predetermined distance from the slider holding means so that the first bonding surface and the second bonding surface are at acute angles to vertical direction, respectively, and so that a virtual line formed by intersecting the surface including the first bonding surface and a surface including the second bonding surface become substantially parallel to a horizontal plane; a vacuum pad that has a sucking opening formed at the top, the vacuum pad being able to suck solder ball held in the ball holding holes into the sucking opening, and the vacuum pad being able to carry and release the solder ball at a position where both the first bonding surface and the second bonding surface can contact or be close to the solder ball; and an optical device to apply the solder ball with condensed beam by condensing inputted laser beam, the optical device having a laser output opening to output the condensed beam, the laser output opening of the optical device being able to access the solder ball close to or in contact with the solder ball, the solder ball contacting both the first bonding surface and the second bonding surface.
The slider holding means may have a plurality of connecting portions consisting of the first bonding surface and the second bonding surface, and the solder-ball holder has ball holding holes in the same number as the number of the connecting portions. The ventilating hole for exhausting gas from the ball holding hole, and injecting gas into the ball holding hole, may be formed on the bottom of the ball holding hole. The vacuum pad and the optical device may be integrally configured.
Furthermore, the optical device may be configured by disposing a condenser lens in the beam path of the laser beam, and forming a nitrogen gas injecting nozzle for injecting nitrogen gas to the side wall that forms a beam path space from the condenser lens to the laser output opening, so that the injected nitrogen gas is discharged out of the laser output opening.
In the method for solder-ball bonding according to another invention, in order to connect a first bonding surface and a second bonding surface by using solder ball, the first bonding surface being on pad formed on a slider held by a slider holding means of a disk device, the second bonding surface being on a pad formed on an end of a lead set on the slider holding means, and the second bonding surface is set substantially perpendicularly to and close to a surface including the first bonding surface, the method comprises the steps of holding the slider holding means so that the first bonding surface and the second bonding surface are at acute angles to vertical direction, respectively, and so that a virtual line formed by intersecting the surface including the first bonding surface and a surface including the second bonding surface become substantially parallel to a horizontal plane; placing a solder ball at a predetermined distance from the first bonding surface and the second surface by a solder-ball holder, the solder-ball holder having a stocker to stock plural holder balls and a ball holding hole to hold solder ball supplied from said stocker in predetermined positions, at a predetermined position; carrying solder ball held in the ball holding hole to a position where both the first bonding surface and the second bonding surface can contact or be close to the solder ball; and applying laser condensed beam to a solder ball, the solder ball contacting both the first bonding surface and the second bonding surface.